Unable to link virgin media account to virgin media O2 ID account

I'm having the exact same issue - new customer. Asked me to create O2 account (I did) then asked to link my virgin media account (which I tried) and got the same message:

"We’ve found your Virgin Media account

However, this account is linked to an email address that’s different to the one on your Virgin Media O2 ID.

If you’d like to continue and link your Virgin Media account to your Virgin Media O2 ID, please confirm the full email address your Virgin Media account is currently registered to.

We’ll then send an email to that email address to approve the transfer."

I also don't understand WHY it is neccessary for me to create O2 account if I want to access MyVirginMedia account for my broadband? I don't even use any service that has anything to do with O2 at the moment.